This invention relates to a multi-stage sprocket assembly, and more particularly to a multi-stage sprocket assembly comprising a cylindrical member and a group of two or more different size sprockets coupled with the cylindrical member at the outer periphery thereof.
Generally, this kind of multi-stage sprocket assembly has at the outer periphery of the cylindrical member a number of axially extending retaining grooves. A screw thread is provided at the outer periphery of one axial end of the cylindrical member and a plurality of sprockets having at the inner periphery of their central bores a number of projections engageable with the retaining grooves, are fit onto the cylindrical member sequentially from a larger diameter sprocket to a smaller diameter sprocket at regular intervals the sprockets being spaced by washers. The smallest diameter sprocket has at its inner periphery a screw thread and is screwed with the screw thread at the cylindrical member. Alternatively, all the sprockets have a screw thread and are screwed with a screw thread formed throughout the outer periphery of cylindrical member. In either case, the sprockets are coupled with the cylindrical member.
Such coupling makes assembly or removal of the sprockets onto or from the cylindrical member difficult, especially when the sprockets have been in use.
The invention has been designed to overcome this problem. An object of the invention is to provide a multi-stage sprocket assembly capable of facilitating coupling or removal of the sprockets with or from the cylindrical member.
The multi-stage sprocket assembly of the invention comprises a cylindrical member and a sprocket group, and a retaining means between them for preventing the sprocket group from axially moving with respect to the cylindrical member. The retaining means comprises an engaging groove extending circumferentially of the cylindrical member and an engaging member elastically engageable with and disengageable from the groove the latter being against the engagement elasticity. The engaging member engages with the engaging groove to mount the sprocket group axially immovably to the cylindrical member and disengages from the groove to remove the sprocket group from the cylindrical member.
The sprocket group of the invention comprises two or more sprockets and one or more ring-like shaped washers for keeping the sprockets spaced at regular intervals, the sprockets and washers being coupled integrally with each other by means of a coupling means. The respective sprockets have a central bore insertable onto the outer periphery of the cylindrical member. At the inner periphery of each central bore are provided projections engageable with retaining grooves which are formed at the outer periphery of the cylindrical member extending axially thereof.
The engaging groove of the retaining means is preferably formed at the outer periphery of the cylindrical member and the engaging member is provided at the sprocket group, for example, at the washer thereof. The engaging member is formed of an elastic wire, having a portion elastically engaging with the engaging groove. Alternatively, a C-like shaped ring of elastic wire separate from the engaging member is formed to catch the engaging member to thereby allow it to elastically engage with the engaging groove through the ring.
According to the invention, the sprocket group is mountable to the cylindrical member in a single operation and is axially immovable with respect to the cylindrical member through engagement of the engaging member with the engaging groove, and is easily and quickly removable from the cylindrical member upon release of the engagement.
These and other objects and novel features of the invention will be more apparent from the following description taken in accordance with the accompanying drawings.